<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <title>定位特殊应用</title>
</head>

<style>
.outer{
  background-color: orange;
  padding: 10px;
  position: relative;
}

.inner{
  background-color: #7bff53;
  position: absolute;

  /*占满父元素 */
  /*越过 padding*/
  top: 0;
  left:0 ;
  right: 0;
  bottom: 0;
}


</style>
<body>

<div class="outer">
  <div class="inner">
inner
  </div>
</div>
</body>
</html>
